August 9, 2005

SUBJECT: Liquidambar Street Trees-Nuisance Fruit Problem – Study Issue

REPORT IN BRIEF

This report is in response to a citizen’s request to have the Council study the issue of the perceived hazard presented by the fruit balls that shed from Liquidambar trees.  A Study Issue paper on this issue (Attachment A) was approved by Council at their January 21, 2005 meeting.

The City of Sunnyvale has a street tree population of 36,875, of which 3,829 are the species Liquidambar styraciflua – American Sweet­gum, locally referred to as Liquidambar.  Liquidambar trees develop fruits that, once mature, fall from the trees.  The period when this is most abundant here in Sunnyvale is during the months of February and March of each year.  There are fruit balls that remain in the tree past this period and can fall from the tree any time of the year but in less abundant quantities.  Street trees including Liquidambar are removed only when they become hazardous.  A hazardous tree is one that the tree itself is an eminent threat of major branch failure or failure of the whole tree, not because of fallen debris. 

Current city policy (Municipal Code 13.08.380 Sidewalk Maintenance; Attach­ment B) is to have the adjacent property owners maintain the landscape at ground level of the public right-of-way (ROW).  The city does not spray trees to control the fruit balls although residents can obtain a free tree work permit to have their Liquidambar street tree sprayed to control the fruit balls on their own. The city does do street sweeping but that service was reduced from a biweekly service to a monthly service in February 2004.  Currently the Street Tree Services program replaces Liquidambar trees, when they have to be removed, with alternate species.  No new Liquidambar trees have been planted in Sunnyvale since the early 1980’s, except where the adjacent property owner has specifically requested that the same tree be replanted.  This has happened less than 10 times since the 1980’s.  The natural loss rate for Liquidambar trees currently is about thirty trees per year.

Citizen outreach efforts had thirty-seven citizens respond to an e-mail sent out to the Neighborhood Associations. Responses were mixed but the two most numerous responses were one, remove the Liquidambars and two, leave the current policy as is and have the adjacent property owners clean up the tree litter.

All options for maintaining fruit balls shed from Liquidambar trees would require a budget modification except maintaining the current policy and allowing property owners to remove trees at their expense.  The tree replacement options included in this study allow for a fixed rate of replacement of Liquidambar trees per year so that over a period of time, the Liquidambar population can be changed out with alternate tree species. 

Staff recommends that the current city policy be maintained.  The current policy will, over time, reduce the Liquidambar street tree population with alternative species without increasing the current funding in the Street Tree Services program.

BACKGROUND

This study was created out of a concern by a Sunnyvale resident in a presenta­tion to City Council on the nuisance of the hard cone-like fruit balls (See Attachment C) produced by the street tree species Liquidambar styraciflua – American Sweet­gum.  The resident noted that he, as well as others in Sunnyvale, have slipped or fallen due to these fruit balls and have received injuries as a result.  He requested that the City Council study the issue to see what could be changed to eliminate or lessen this potential for injuries resulting from these fruit balls.

Street Tree Inventory

City street trees are those trees in the public right-of-way (ROW) and in the Street Tree Services Program electronic database.  They are planted into either of two locations depending if the public sidewalk is monolithic (attached to the curb) or if the sidewalk is at the back of the ROW and there is a strip of land between the curb and the sidewalk referred to as the ‘Parkway Strip’ (See Attachment D).   

The City of Sunnyvale has an excellent history with urban tree care.  Ever since the early 1980’s the Street Tree Service Program has employed the standards of the International Society of Arboriculture (ISA) in caring for its urban trees.  Currently the street tree inventory has a total of 36,875 trees.  Of that, there are 3,829 Liquidambar styraciflua – American Sweet Gum.  Liquidambar is the second most numerous species in the Sunnyvale inventory at 10.4% of the street tree population.  Liquidambar is only exceeded by Magnolia grandiflora – Southern Magnolia which comprises 12.8% of the street tree population (4,708 trees).  Interestingly, Magnolia and Liquidambar make up nearly one quarter of all Sunnyvale street trees (23.1%).  The top twelve street tree species make up 56% of the inventory.  The listing shown as Attachment E, shows the distri­bu­tion of the top 30 most numerous tree species.  These 30 species make up 80% of the street tree inventory.

Liquidambar Characteristics

Liquidambar street trees in Sunnyvale for the most part are mature trees.  Most of the trees are at least 25 years old with many approaching 45 years of age.  Liquidambar trees are distributed throughout Sunnyvale.  Residential streets south of Evelyn Avenue have the most Liquidambar trees.  El Camino Real is the main commercial street with Liquidam­bar as the primary street tree. The Liquidambar population is relatively low north of Evelyn Ave except for some streets in Lakewood Village.  (See Attachment F for a distribution map of Liquidambar street trees in Sunnyvale)

Liquidambar trees have several significant features.  The Liquidambar is best known for its vibrant colored fall maple-like foliage.  Liquidambar is also known for numerous shallow roots that cause uplifted concrete, public and private, as well as fill front lawns with exposed surface roots.  Liquidambar also is known for its abundant hard cone fruit balls.

The mature fruit ball is a hard spherical, one inch plus diameter cone with spike projec­tions (see Attachment C).  The fruit balls can fall from the trees anytime of the year but they are shed primarily here in Sunnyvale in the months of February and March at about the same time that the tree sets out flowers and new spring foliage (See Attachments G and H.)

Current City Practice

The City maintains the City street trees and other utilities in the public right-of-way (ROW).  The City does not maintain the ground level landscape in the off-the-street portion of the public ROW.  Currently the policy leaves all ground level maintenance of public ROW from the face of the curb back to the private property line to be the responsibility of the adjacent property owner.

The City performs street sweeping of the curbside road edge currently on a monthly basis. There are no seasonal ‘extra’ sweepings, al­though there are more staff hours dedicated in the fall season to pick up leaves left either by residents or by the sweeper operators.  This extra staff removes piles of leaves using tractors and dump trucks.

Prior to Fiscal Year 2003-04, the street tree program annually provided pest control services on street trees, which included chemical hormone treatments on approximately 150 Liquidambar trees or less than 4% of the Liquidambar tree inventory.  This hormone treatment aborted the fruit balls as they formed in March.  As a budget saving measure commencing FY 2003-04, the street tree pest control program was eliminated, saving $21,736 annually. The Liquidambar spray treatments were only a portion of the pest program and the Liquidambar treatments were not tracked separately within the budget.  It is estimated that $11,000 of the total pest control program was for Liquidambar fruit control treatments of this limited number of trees.  Since July 1, 2003, no Liquidambar trees have been treated for fruit elimination as part of Sunnyvale’s service level reductions.

Liability and Claims History

The Risk and Insurance Division of the Human Resources Department maintains records for seven years and reports that from 1998 to 2005, the City of Sunnyvale has had five trip and fall claims due to Liquidambar fruit balls.   This averages out to a little less than one claim per year.  The City has denied three claims, paid one claim, and one claim for this year (2004-05) is still open.  As of this writing, the total amount paid out on Liquid­ambar claims since 1998 is less than one hundred dollars.  No legal fees have been used for these claims. 

Residents frequently ask whether they are legally responsible for personal injuries or property damage if someone falls on a Liquidambar ball in front of their house. Of course, the City cannot provide legal advice to individual homeowners about their potential liability as the City may be in a position of looking to the homeowner for indemnity if the city is sued, it would be a conflict of interest.  That said, the City can discuss general legal principles that would apply to sidewalk liability.   There is, however, no “one answer fits all” response to this inquiry. 

First, Streets and Highways code section 5610 provides in relevant part:

The owners of lots or portions of lots fronting on any portion of a public street or place when that street or place is improved or if and when the area between the property line of the adjacent property and the street line is maintained as a park or parking strip, shall maintain any sidewalk in such condition that the sidewalk will not endanger persons or property and maintain it in a condition which will not interfere with the public convenience in the use of those works.

Consequently, an adjoining homeowner has a duty under state law to maintain adjacent sidewalks in a safe condition.  If Liquidambar fruit balls fall on the sidewalk, the homeowner has a duty to remove them before they become a hazard.  But, if someone were to trip and fall on a Liquidambar ball, under California court decisions the Streets and Highways Code provision does not create a duty to a pedestrian and automatically provide a legal basis for claiming personal injury damages. 

A homeowner could be liable for injuries resulting from a slip and fall on Liquidambar balls if the injured person could demonstrate that the homeowner both knew of pedestrian use of the sidewalk and failed to take reasonable precautions to keep the sidewalk safe with notice of Liquidambar balls creating a dangerous condition.  In the alternative, some cities (i.e. San Jose) have passed an ordinance imposing liability on homeowners for personal injuries resulting from their failure to maintain the sidewalk in a safe condition.  Sunnyvale has not enacted such an ordinance, although it could do so.   While homeowner liability will depend on the specific facts of each incident, homeowners are encouraged to call their individual homeowner’s insurance carriers for specific advice on their policy coverage.

The City of Sunnyvale, as a general policy and in the interest of its taxpayers, would not accept any liability for damages resulting from slips or falls on Liquidambar balls on sidewalks or streets in front of private property.  The California Government Tort Claims Act does provide, under certain conditions, for public entity liability for dangerous conditions on public property.  An injured person would need to demonstrate that the injury resulted from a dangerous condition of public property, and that it occurred because of a negligent act or omission by the public entity.  Again, any claimed City liability for Liquidambar fruit ball injuries would be highly fact-specific and the City under almost all circumstances would deny any liability. 

EXISTING POLICY

Chapter 13.08.380 Sidewalk Maintenance of the Sunnyvale Municipal code (See Attachment B) requires property owners adjacent to the public street to maintain the public sidewalk and the parking strip between the sidewalk and the street free and clean of excessive amounts of leaves, trash or other debris.
The city does not provide ground level maintenance of the ROW except for street sweeping.

Chapter 13.16 – Street Trees of the Sunnyvale Municipal Code provides for removal of hazardous trees (13.16.080 – Removal of damaged trees, Attachment I).  This section has been interpreted to mean that the tree itself has to be an eminent threat of major branch failure or failure of the whole tree to be deemed a hazard.  Natural litter, including Liquidambar fruit balls generated by an otherwise healthy, vigorous tree has not categorized a tree to be hazardous.

Since the early 1980’s, the Street Tree Services program has not initiated any new street tree plantings of Liquidambar trees.  There have been a few Liquidambar trees replaced, upon request by the adjacent property owner, when the existing tree had to be removed for safety reasons.  Otherwise, the Street Services program now replaces Liquidambar street trees with alternative tree species when they have to be removed.

DISCUSSION

All trees produce some type of litter, such as: leaves, needles, cones, fruits, seedpods, nuts, flowers, etc., whether deciduous or evergreen.  Liquidambar typically does not produce its character­istic fruit balls for the first fifteen to twenty years.  Once a Liquidambar begins producing flowers and fruit, it will continue for the remainder of its life.  Therefore, as a Liquidambar grows older and larger the number of fruit balls it produces increases.  Liquidambar is native to the eastern US, ranging from Connecticut to Texas, primarily east of the Mississippi River.  In its native range it can reach 150 feet tall and can live over one hundred and fifty years.  In cultivation Liquidambar typically can get to sixty to eighty feet.  Here in Sunny­vale our largest trees are in this range.  (See Attachment J – Harvard Avenue).  In cultivation, urban settings, the lifespan is less. 

The hard cone-like fruit ball can roll easily when stepped upon.  Also the spiked projections of the balls can be painful if stepped on by bare feet.  The dilemma is how to reduce the number of fruit cones that can be stepped on.  There are several methods described in detail below.   These include:

     •   Routine removal of fruit balls – raking, mowing, vacuuming, blowing, sweeping

     •   Abort immature fruit – chemical hormone treatment

     •   Pruning – reduce branches that bear the fruit balls

     •   Tree removal – remove the entire tree and replace with alternate species

Routine removal of fruit balls

Currently the adjacent property owners are responsible for the litter removal in the public right-of-way (ROW) excluding the street although they are encour­aged to remove organic litter and recycle it in their yard waste toters. 

The City sweeps the streets and that removes some of the fruit balls.  But as of February 2004 street sweeping moved from a biweekly service to a monthly service as part of FY 2003-04 service level reductions.  Over the course of the heaviest fruit ball drop season, February - March, fruit balls shed directly by the Liquidambar as well as those blown or raked into the street by property owners only get picked up twice during this two-month period of time.

Liquidambars do not shed all of the previous year’s fruit balls in the late winter.  Some fruit balls hang up in the tree and will continue to fall over the summer while the current year’s fruit balls mature.  Green, immature fruit balls can also fall from the trees during the summer and into the fall.  Fruit balls that get raked or blown into the street will accumulate there between street sweepings.

Since Liquidambar trees are not on all streets in Sunnyvale, if directed, extra sweepings done in February and March would cost less than complete citywide sweepings but would require a change to all existing sweeping schedules.  Supple­men­tal street sweeping specifically for Liquidambar trees will set a precedent.  This precedent could lead to requests for other street tree species to have special supplemental sweeping. 

With 3,829 Liquidambar trees it is impractical and uneconomical to have city staff remove litter shed by these trees other than by street sweeping.   Since all of the City’s street trees shed litter routinely, the city must rely on individual and business property owners to maintain the public ROW.  Increasing street sweeping during the late winter could assist property owners but street sweepings cannot be recycled; they must go to landfill.  Debris from the street blended with tree litter is unacceptable in the green waste recycling process.  Street sweeping alone will not remove the Liquidambar fruit balls from private property.  Property owners are encouraged to continue to recycle organic debris in their yard waste toters including green waste that falls in the street.

For property owners who cannot physically clean up the litter this presents a problem.  These owners must have someone else do this for them.  Those who have the resources can pay for maintenance work; others may be on limited or fixed incomes and cannot.  In our outreach correspon­dence some respondents suggested neighborhood volunteers or neighborhood children to assist those who could no longer maintain their landscaping themselves.

Abort immature fruit - Chemical Treatment

There is a registered synthetic hormone available that if applied at a precise time in the fruit development stage, will force the Liquidambar to abort 95%+ of the developing fruit balls.  The material goes by the trade name of ‘Florel’.  The actual chemical is called Ethephon.  This material induces the natural process of abscission which takes place when cellulose in the cells break down and plant parts are shed i.e. leaves, flowers, fruits etc.

The timing of treatment for Liquidambar is critical.  The tree must be sprayed when it has fully developed the flowers and the first set of new leaves is about the size of a silver dollar (See Attachment H).  Spraying too early or too late makes the treatment ineffective.  The window of opportunity for this is about three weeks, and there is variability among individual trees and areas within a single tree.  Shading and tempera­tures will affect the development of the flowers. Considering the timing and temperature issues, overall the treatment to abort the Liquidambar fruit was successful. Because we were only treating 150 trees, we had the capacity to treat these trees within this narrow window of opportunity.

Economically this method of fruit control is expensive.  The cost per tree with chemical and labor cost from a private contractor ranges from $50 to $150 depending on the size of the tree.  For example, using a cost to treat a fifty foot tree at $98 each, the annual cost for this type of treatment for all 3,829 trees would be approximately $375,242.  As Liquidambar trees are replaced, the annual cost would decrease.  This treatment only affects the current crop of fruit balls, thus requiring it to be done annually.   The second problem is timing.  With such a small window for treatment, treating all Liquidambars verses the previous budgeted amount of approximately 150 trees, would not be possible without assistance from multiple outside contractors or adding at least 3,450 staff hours as well as purchase or rent additional equipment to do this in-house.  Also, treating all Liquidambar trees would increase the problem of spray drift onto homes, gardens and vehicles.  Prompt and proper notification of homeowners would be critical to avoid these issues.  In addition, to avoid pedestrian traffic during treatments, this operation was performed at night when done in-house, whereas a contractor would most likely perform this operation during daylight hours.

The Street Tree Ordinance does allow private property owners to work on street trees.  The Street Tree Services program does issue work permits to individual owners to treat their street tree(s).  The permit is free but is conditional on having professionals to provide the service and show proof of licensure and appropriate insurance.  The fee to treat a tree by a private contractor ranges from $50 to $150 per tree primarily depending on the size of the tree.

Pruning

Pruning is an option but like the chemical treatment it is expensive and is less effective than the hormone treatment.  Flowers are borne at the leading buds of new spring growth.  Heavy pruning to stimulate new vegetative growth will reduce the number of fruit balls produced.  The tree diverts stored energy reserves into new vegetative growth rather than moving those reserves to develop flowers and fruit.  This effect is only temporary for the current year’s growth.  The second year the tree will have recovered and will set flowers and fruit as before.  Even with heavy pruning there still will be fruit balls that develop.

The street tree pruning cycle was changed from a four and one half year average to a five and one half year average in Fiscal Year 2003-04.  The number of trees pruned annually was reduced from 7,780 trees per year down to 6,454 trees per year as part of the cost saving service level reductions implemented in that fiscal year.  Pruning resources are best directed to pruning of whole trees to make the trees structurally stronger rather than to control fruit development.

Tree Removal and Replacement

Tree removal had some interest from our outreach correspondence.  For most who responded in favor of removal, it appeared that they had lived with a Liquidambar tree for quite some time and were getting weary of the mainte­nance required.  Surface roots and raised concrete by roots were also added by many as additional reasons for being in favor of removal. 

Since the early 1980’s, Liquidambar trees that had to be removed have not been replaced with Liquidambars. Since then, the inventory of Liquidambars has declined.  The rate of removal is at or a little less than one percent of the population, i.e. 20 to 30 trees per year.  Over the past fifteen years between 350 and 400 Liquidambars have been removed and replaced with alternate species.  If this policy continues, the Liquidambar population will decline.  With age, the Liquidambars are expected to have failures that will force their removal at a higher rate.  As time progresses, the most resilient trees will persevere and the rate of decline will slow.  Still in the best of urban settings, the impacts of intrusions into the tree’s environment will cause them to decline.  It is estimated that continuing the current policy, within seventy-five to one hundred years the Liquidambar population in the street tree inventory will be nearly eliminated. 

Since Liquidambar street trees in Sunnyvale are mature trees, removal, especially along whole streets, would have an immediate environ­mental as well as aesthetic impact.  Large trees clean the atmosphere, removing large amounts of carbon dioxide while releasing oxygen back into the atmosphere.  Also, shade that large trees provide, reduce the heat island created by urban areas.  The summer shade created by large tree canopies makes Sunnyvale a more comfortable place to live.  Dust and other particulates get trapped on foliage surfaces making the air cleaner than without large trees.

An alternative to removal of entire blocks of Liquidambar trees would be to allow individual property owners to remove City Liquidambar street trees adjacent to their property and replace the tree with an approved alternative species, with all expenses paid by the property owner. This would allow those homeowners who wish to keep their Liquidambar tree to do so and not impact the aesthetics of an entire block. 

Good urban forestry practice is not to have any more than five percent of any one-tree species in your street inventory.  This avoids losses when catastrophic conditions occur, i.e. freezes, insect or disease infestations such as the loss of American Elms to Dutch Elm Disease in Midwest and Eastern US.  With Sunnyvale having about ten percent of the street tree population as Liquidambar, our street tree inventory is over the urban forestry standard of five percent.  At 3,829 Liquidambars in our street tree inventory, approximately 1,900 Liquidambars could be removed and replaced with alternate species bringing the inventory within the five percent standard.

Tree replacement should be done slowly as to not denude and aesthetically impact Sunnyvale’s neighborhoods of trees.  The removal process can be accomplished by having the City Arborists be more critical in determining which trees should be candidates for removal and replacement.  Growth rate of the replacement trees should determine the replacement rate on any one street.  Slower growing replacement trees will increase the time to convert the street to the alternate species; conversely faster growing trees would allow for a shorter time.

Another factor to consider is the impact Liquidambar roots have on sidewalks, curbs, and driveways.  This factor is not exclusive to Liquidambar; most trees planted in close proximity to concrete flatwork will affect the concrete in time.  When new trees are installed, the tree program installs root barriers to lessen the impact tree roots have on concrete.  Even with root controls installed, adjacent concrete can be impacted in time.

Removal and replacement of Liquidambar street trees at a fixed rate will provide a known period of time to meet a specific goal.  If the goal is to reduce the Liquidambar trees down to five percent of the inventory a fixed annual removal rate would fix a time period to meet this goal.  The same is true if all Liquidambar trees are to be replaced as a goal.  To bring the Liquidambar inventory down to the five percent level, a removal rate of seventy-five trees per year would take twenty-five years.  At a one hundred trees per year rate this would take twenty years.  If the goal is to remove all the Liquidambars in time, it would be fifty years and forty years respectively.

Removal and Replacement Options Matrix for Liquidambar

          •   Replace all trees at 75 trees per year – duration 50 yrs

          •   Replace all trees at 100 trees per year – duration 40 yrs

          •   Replace to 5% level at 75 trees per yr – duration 25 yrs

          •   Replace to 5% level at 100 trees per yr – duration 20 yrs

Other Municipalities

An information request e-mail was sent out to other municipalities through the California Department of Forestry’s urban forestry network.  The information request asked if their community had a Liquidambar street tree popula­tion, how many street trees they have in their total street tree inventory and what they did with the Liquidambar trees to control the fruit balls if anything.  There were sixteen responses received, fifteen California cities and Seattle, WA.  The respondents include:

              •   Campbell, CA

              •   Chowchilla, CA

              •   Grand Terrace, CA

              •   Inglewood, CA

              •   Lawndale, CA

              •   Livermore, CA

              •   Los Angeles, CA

              •   Modesto, CA

              •   Oakland, CA

              •   Pasadena, CA

              •   Petaluma, CA

              •   Pleasanton, CA

              •   Rancho Cucamonga, CA

              •   Redwood City, CA

              •   Stockton, CA

              •   Seattle, WA

The responses can be categorized as follows:

-  Property Owners Responsible – no services by city except street sweeping

-  Tree Removal and Replacement by property owner – with city approval

-  Removal by City – in high traffic commercial areas.

- No New Liquidambars – alternative tree species or use the cultivar ‘Rotundiloba’

-  Chemical Hormone Spray Treatment – small programs, not on all trees

Eleven of the sixteen respondents stated that they do not provide any special fruit ball clean up service except for street sweeping.   These cities require property owners to maintain the public right-of-way.  The other respondents did not comment on the responsibilities of the adjacent property owners.

Two cities have a tree replacement program where the residents must pay all costs.  Both cities require approval by the city before the property owner can remove a city tree.  This program is new for the City of Redwood City and does not have much history yet.  Campbell allows residents to appeal to the Parks and Recreation Commission if the staff Arborist denies the removal. 

The city of Chowchilla commented they removed Liquidambars in high traffic areas.  No other city had a program of tree removal for fruit or litter control. 

Six of the cities responded that they do not plant any new Liquidambars.  Some cities allow the cultivated variety Liquidambar ‘Rotundiloba’.  Rotundiloba is known to not produce fruit balls. The leaf lobe tips are rounded as compared to pointed for Liquidambar sytraciflua. Also Rotundiloba’s fall foliage is a uniform dark burgundy color.  Species other than Liquidambar are also planted as new or replacement street trees.

Two cities commented on the use of chemical hormone spray treatment.  Livermore’s program is experimental.  Modesto did not elaborate on the extent of their use of spray treatment.

The City of Los Angeles responded that their street tree inventory is 700,000 with 42,000 of those being Liquidambar styraciflua.  Los Angeles has an ordinance that stipulates cleaning up fruit droppings is the responsibility of the abutting property owner.  The Chief Forester cautions that providing special treatment for one tree species will lead to the possibility of litigation on other species with fruit droppings.

FISCAL IMPACT

The various options have a fiscal impact except Sunnyvale’s current policy of having the adjacent property owners maintain the public right-of-way. 

Chemical Hormone Spray Treatment

The estimated cost average per tree to be treated is around $98, bringing the cost to spray all Liquidambars to $375,242 annually.  The total cost of $375,242 was estimated based on the assumption that 0.9 staff hours would be required per fifty-foot tree for the spray treatment.  Material cost (Florel) is estimated at approxi­mately $45 per tree.  Treatment includes preparation time, property owner notification (door hangers plus no parking barricades), clean-up, admin­istra­tive duties - pesticide reporting (state law), supervision and oversight.  Approxi­mately $13,000 in additional equipment (spray rigs, trucks) and a 15% contract contingency has also been included in the cost estimate.

Street Sweeping

To determine the cost for supplemental street sweeping, we would need to reevaluate our existing street sweeping schedules to determine if we could provide this service with existing street sweeping equipment, or if we would be required to acquire additional equipment.  An alternative would be to contract out this service.  The cost of supplemental sweeping could range from $20,000 to $125,000 annually depending on the scope of the service and the type of nuisance tree drop debris that were to be removed. This range includes a very limited sweeping service of selected streets to the restoration of biweekly sweeping of the entire city.

Tree Removal and Replacement

There are four options considered with regard to the replacement of Liquid­ambar trees.  These removal options would require additional staff hours and additional equipment.  The stump removal and the new tree planting costs would need to be added to our stumping and planting contract.  The non-inflated cost per tree replaced would average out to $1,210 each.

The total cost of tree removal was estimated based on the assumption that 18 staff hours would be required per tree for the removal and cleanup of the aerial portion of the tree.  The cost of the replacement tree is $45 per tree. Contracted stump removal and new tree planting is estimated at $310 per tree removed.  The tree removal and replacement process includes preparation time, property owner notification (door hangers, no parking barricades), clean-up, admin­istrative supervision and oversight.  A 15% contract contingency has also been included in the cost estimate.

Removal and Replacement Cost Matrix for Liquidambar

Conclusion

Liquidambar is one of the dominant street tree species in Sunnyvale.  It makes up a little over ten percent of the trees in the inventory.  Liquid­ambars, along with all of the other street trees in Sunnyvale produce litter.

Chemically treating Liquidambar to abort its fruit is only a temporary measure to control fruiting of these trees.  The trees must be treated each year at a relative high cost.  The chemical spray treatment still could be available to individuals to treat their own trees to control the fruit ball formation at their own expense while the product is available.

With structural pruning services reduced beginning in Fiscal Year 2003-04, all pruning resources should be reserved for structural pruning not fruit control.

Increasing the removal rate of Liquidambar is an option.  By fixing the removal rate you can predict the time to complete the set goal.  The goal for removal and replacement can be to remove all Liquidambar trees or just down to a five percent inventory level (about 1,900 trees).  Once the goal is set, fixing the removals to 75 or 100 trees per year, will give you a predictable duration to meet the goal.

PUBLIC CONTACT

The public was given opportunity to comment on the Liquidambar fruit ball issue.  The first public contact was on May 4, 2005 with the City’s Urban Landscape Supervisor attending a meeting of the Birdland Neighbors Association.  A presentation of the Liquidambar Nuisance Fruit issue was one of the agenda items.  Attendees made comment as well as asked questions.  Notes regarding this issue taken at the meeting are included in Attachment K. 

All of the Sunnyvale neighborhood associations were contacted through the Community Outreach Coordinator’s e-mail contact system.  From that request staff received thirty-seven e-mails from various citizens including two Planning Commissioners.  The specific e-mails are on file as not to violate the privacy of the individual respondents.  The comments and suggestions are categorized as follows:

          •   Remove Trees to eliminate fruit balls – City pays all costs (12)

          •   Maintain current policy – residents responsible of clean-up (10)

•   Spray trees to control fruit (8)

•   Increase street sweeping (3)

•   No opinion on solution (2)  

§         Remove Trees to eliminate fruit balls – Residents pay or share cost with city (2)     

          •   Scheduled Replacement – replace trees over a planned period (1)

          •   Eliminate city staff provided tree service and contract out (1)

          •   Neighborhood volunteers to help elderly maintain litter. (1)

The number in the parenthesis indicates the number of respondents with that category of comment or suggestion.  Some respondents had multiple comments.

The two categories receiving the most responses are in opposing camps.  Both groups in general were very adamant about their point of view.  Those wanting the trees to be removed in general did not oppose having trees but the Liquidambar itself was in their opinion a hazard and a heavy maintenance burden.  Several of those who desired to keep the current policy were quite incensed that the City would consider removing the street trees and appalled that residents did not want to do their civic duty to maintain their property.

ALTERNATIVES

Alternatives #1 and #7 do not require budget modifications.  If Council chooses any of the alternatives requiring budget modification, they would need to identify the funding source(s) for said alternative(s).

1)  Maintain the current policy which requires property owners to maintain the litter in the public right-of-way that is generated by city trees.  When trees have been determined by the City Arborist to be unhealthy or are diseased and are a physical hazard, they shall be removed and replaced with an alternate tree species other than the existing species, Liquidambar styraciflua.  (No budget impact)

2)  Increase the rate of Liquidambar styraciflua removal from the current loss rate to the removal of seventy-five trees per year until the inventory of Liquidambar trees has been reduced to less than five percent of the entire street tree inventory and replaced with alternate species. (Reduces Liquidambar inventory to 1,845 in 25 years.  Budget modification required – Add $90,750 per year. Total non-inflated cost over 25 years: $2,268,750)

3)  Increase the rate of Liquidambar styraciflua removal from the current loss rate to the removal of seventy-five trees per year until the inventory of Liquidambar trees has been has been replaced entirely with alternate species. (Removes all Liquidambar from tree inventory in 50 years. Budget modification required – Add $90,750 per year. Total non-inflated cost over 50 years: $4,537,500)

4)  Increase the rate of Liquidambar styraciflua removal from the current loss rate to the removal of one hundred trees per year until the inventory of Liquidambar trees has been reduced to less than five percent of the entire street tree inventory and replaced with alternate species. (Reduces Liquidambar inventory to 1,845 in 20 years.  Budget modification required – Add $121,000 per year. Total non-inflated cost over 20 years: $2,420,000)

5) Increase the rate of Liquidambar styraciflua removal from the current loss rate to the removal of one hundred trees per year until the inventory of Liquidambar trees has been has been replaced entirely with alternate species. (Removes all Liquidambar from tree inventory in 40 years.  Budget modification required – Add $121,000 per year. Total non-inflated cost over 40 years: $4,840,000)

6) Treat all Liquidambar street trees with the chemical hormone treatment ‘Florel’ to abort immature developing fruit balls during the month of March each year. (Budget modification required – Add $375,242 per year)

7)  Allow individual property owners to remove any size City Liquidambar street tree adjacent to their property and replace the tree with an approved alternative species planted as a thirty-six inch standard nursery boxed sized tree with all expenses paid by the property owner.  Removal shall require an approved tree work permit issued by the Superintendent of Trees and Landscaping.  (No budget impact).

8)  Direct staff to perform an evaluation for a supplemental street sweeping to determine the feasibility and cost to add additional street sweeping to city streets with Liquidambar street trees.  (Cost ranges from $20,000 to $125,000 depending on scope of service.) 

RECOMMENDATION

Staff recommends Alternative #1 - Maintain the current policy which requires property owners to maintain the litter in the public right-of-way that is generated by city trees.  When trees have been determined by the City Arborist to be unhealthy or are diseased and are a physical hazard, they shall be removed and replaced with an alternate tree species other than the existing species, Liquidambar styraciflua. 

Reviewed by:

Marvin A Rose, Director, Public Works

Prepared by: Leonard E. Dunn, Urban Landscape Supervisor

Approved by:

Amy Chan